Cannabis or marijuana is usually smoked and typically mixed with tobacco. It can interact with certain types of antidepressants, such as tricyclic antidepressants (TCAs), which share similar side effects.

Cannabis and antidepressants

Cannabis or marijuana can interact with tricyclic antidepressants (TCAs), such as amitriptyline, imipramine and dothiepin.

Both cannabis and TCAs can cause an abnormally fast heartbeat (tachycardia) and high blood pressure (hypertension). There's also a risk of other side effects, such as confusion, restlessness, mood swings and hallucinations.

There's a risk that using cannabis while you're on any of these medicines could lead to problems such as tachycardia, even if you don't already have a heart condition.

Little research has been done into the interaction of cannabis with other types of antidepressants, such as SSRIs.

Cannabis and lithium

Lithium is used to treat bipolar disorder, a condition where people can switch between depression and extreme excitement and agitation (mania).

There's little evidence to suggest that people who use cannabis should normally not take lithium, but this hasn't been properly researched.

Side effects of cannabis

It's not clear how often cannabis itself can cause anxiety or depression, but research suggests this can happen.

It's therefore recommended that if you're anxious or depressed and you use cannabis regularly, you should try giving up and see if that helps.